Option 1:
a.) Do I have to do both of these?
Tools>Privacy>Clear Data>Clear HistoryTools>Privacy>Clear Data>Clear URL Bar History
b.) How often do I have to clear them?
c.) Which values must I not exceed for these (Preferences>History):
Keep a list of pages visited in the last X days.Keep a list of X most recently visited locations.
Option 2:
You mentioned, in lieu of the above, compiling the code freshly.
I don't know how to do that. I presume that I am setting some
history value differently (to solve the bug) and then compiling
that changed source to a new EXE. I didn't see steps for that
in the link you provided.

Quoteguenter
1.) I did not find this bug in the bug tracker.
Under which description or bug number is it listed?

No, there is no one open.

I was going to, but I didn't create it. Lazy me.

The bug consists in what Sirias told me in the past in my rants about switching to 1.6. I didn't know it happened to 1.5.

Anyway, the fix recommended is to clear History, what I will not.

But, to clear the bug, it happens when you type a character that has too much references in a cross check to the full history. Why does a full check with the history, is where it is the bug, because, for example, in 1.1.6, didn't happen and probably the checks were too against the full history.

So, with that behavior, when you type a character, or, better said, an string, that matches lots of entries, there is a memory overflow and crashes.

For example, in 1.6b2 happens to me a lot. I tend, as is normal to every internet user, to write www.whatever.com. When you type www., comes the memory overflow (loads of matches for www., what is normal, by the way) and crash. No time for crashreport plugin to catch the error.

Thanks, Guenter and JohnHell, for responding most recently, and thanks to all who kindly took the time to comment on this bug.

I shall clear and reduce the history kept, per your advice, Guenter.

JohnHell, I am glad that you documented this issue via the bug report.

I hope that the wizards who program K-Meleon will fix this vexing bug, which manages to escape being reported in any crash report.

A few final thoughts...

Contrary to Microsoft's press releases that diminish it, there is a significant audience of Windows customers who do not use later versions of the product. Whether because of personal preference; lack of funds to buy everything all over again; limited older hardware; etc., these neglected customers may find refuge in helpful, community-supported software like K-Meleon that does not abandon them.

As a Windows 2000 user who has hardware drivers and diverse software that continues to be fully functional (and, often, still supported and updated), I have paid particular attention, over the years, to apps that still work great for Windows 2000. For some of them, a new version is subsequently released that breaks this compatibility, but not for any technically necessary reason: The break is due to nothing more than something akin to a default compiler setting imposed by Microsoft, put there to slip by developers silently and later frustrate customers and compel them to upgrade to XP (or later). For example, the build is now referencing some XP-only DLL that is totally irrelevant and unnecessary, and this dooms backward compatibility. The developer may not even realize this break, or, if he does, resign himself to labeling the newly compiled version with the requirement "XP or later" (perhaps, subconsciously buying in to Microsoft's PR fiction that "everyone is on XP, by now.")

QuoteTerminator
As a Windows 2000 user who has hardware drivers and diverse software that continues to be fully functional (and, often, still supported and updated), I have paid particular attention, over the years, to apps that still work great for Windows 2000. For some of them, a new version is subsequently released that breaks this compatibility, but not for any technically necessary reason: The break is due to nothing more than something akin to a default compiler setting imposed by Microsoft, put there to slip by developers silently and later frustrate customers and compel them to upgrade to XP (or later). For example, the build is now referencing some XP-only DLL that is totally irrelevant and unnecessary, and this dooms backward compatibility. The developer may not even realize this break, or, if he does, resign himself to labeling the newly compiled version with the requirement "XP or later" (perhaps, subconsciously buying in to Microsoft's PR fiction that "everyone is on XP, by now.")

QuoteJohnHell
So, with that behavior, when you type a character, or, better said, an string, that matches lots of entries, there is a memory overflow and crashes.

For example, in 1.6b2 happens to me a lot. I tend, as is normal to every internet user, to write www.whatever.com. When you type www., comes the memory overflow (loads of matches for www., what is normal, by the way) and crash. No time for crashreport plugin to catch the error.
EDIT: bug reported

I marked it as k-meleon bug because I don't know at what extent may be the history plugin the only responsible of the crash.

It is already in CVS.
This bug was fixed last year in urlbar.cpp Revision 1.18.